Expandable spinal fusion cage

ABSTRACT

A device, system, and method for performing a spinal procedure. The device includes first and second shape-memory outer platforms, the outer platforms expanding at a temperature greater than the transformative temperature, a core member having first and second expansion bodies and first and second wedge members, the first expansion body being coupled to the first outer platform and the second expansion body being coupled to the second outer platform, and a screw rotatably disposed within the core member, the screw passing through at least a portion of each of the first and second wedge members. Rotation of the screw causes the first and second wedge members to move toward each other and the first and second expansion bodies to move away from each other. Thus, reaching a transformation temperature and rotating the screw expands the device to come in contact with and anchored against both of the adjacent vertebrae.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. patent application Ser. No. 14/258,149,filed Apr. 22, 2014, entitled EXPANDABLE SPINAL FUSION CAGE, which isrelated to and claims priority to U.S. Provisional Patent ApplicationSer. No. 61/821,987, filed May 10, 2013, entitled EXPANDABLE SPINALFUSION CAGE, the entirety of all of which is incorporated herein byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

n/a

FIELD OF THE INVENTION

The present invention relates to a method, system, and device forperforming spinal fusion procedures with minimal anatomicalmanipulation. Specifically, the present invention relates to a method,system, and device for preparing an intervertebral space for spinalfusion or other medical procedure, implanting a device such as anexpandable spine cage, and/or introducing and depositing material suchas bone graft material, stem cells, antibiotic, and the like to anintervertebral space.

BACKGROUND OF THE INVENTION

Spinal fusion (also called spondylodesis or spondylosyndesis) is asurgical procedure by which two or more adjacent vertebrae are joined orfused together. This method is primarily used to reduce or eliminatepain caused by abnormal motion of the vertebrae from conditions such asscoliosis, degenerative disc disease, spondylolisthesis, kyphosis,spinal stenosis, fractures, infections, tumors, and other degenerativespinal conditions or conditions that cause instability of the spine.

In interbody fusion, a commonly performed type of spinal fusion, amedical device called an interbody fusion cage or spine cage issurgically inserted between adjacent vertebrae to maintain spinealignment and disc height. Additionally, graft material harvested fromthe patient (autograft) or from a donor (allograft) is inserted into theintervertebral space with the spine cage to encourage the naturalosteoblastic process and resulting fusion between the endplates of thevertebrae. Pedicle screws may also be used to augment the fusion.

Interbody fusion methods that access the vertebrae through the patient'sback (rather than an anterior approach through the abdomen), such as theposterior transpedicular approach, typically involves muscle dissectionfrom the back of the spine in order to create enough space to insert oneor two spine cages. The spine cage has a diameter that is equal to thedesired distance by which the vertebrae are to be separated, and sosignificant manipulation of the anatomy surrounding the vertebrae mustbe performed. Not only are the spinal muscles stretched, moved, or cut,but parts of the ligament flava, which connect the laminae of theadjacent vertebrae, around the implantation site are cut away from thelaminae and removed. Additionally, parts of the laminae and/or pedicleabove and below, and parts of the facet joints on either side, of theimplantation site are removed to increase access. Finally, a substantialportion of the intervening disc is removed and the endplates of theadjacent vertebrae rasped or roughened.

Unsurprisingly, the posterior transpedicular approach is very traumaticto the patient. Not only is there a long recovery time, but the patientmay experience significant amounts of pain immediately following theprocedure. Further, the procedure compromises the ligaments and musclesthat aid in spinal stability, strength, and function. Other knownprocedures, such as transforaminal interbody fusion methods (TLIF),posterior lumbar interbody fusion methods (PLIF), and lateral andanterolateral transpsoas fusion methods may be equally traumatic to thepatient. For example, such procedures may easily result in nerve,ligament, bone, and/or soft tissue damage.

It is therefore desirable to provide a spinal implantation device andmethod that requires less anatomical manipulation, a smaller insertionspace, and is less traumatic than currently known methods.

SUMMARY OF THE INVENTION

The present invention advantageously provides a method, device, andsystem for spinal medical procedures that require less anatomicalmanipulation, a smaller insertion space, and is less traumatic thancurrently known methods. In one non-limiting embodiment, anintervertebral medical device may include a core member, a screwrotatably disposed within the core member, and a first outer plate and asecond outer plate, each of the first and second outer plates beingcoupled to at least a portion of the core member. The first and secondouter plates may be composed of a shape memory material, and may betransitionable between a non-expanded configuration and an expandedconfiguration. For example, the first and second outer plates maytransition to the expanded configuration when the temperature of thefirst and second outer plates is greater than a transformativetemperature of the shape memory material. The core member may include afirst expansion body coupled to the first outer plate and a secondexpansion body coupled to the second outer plate and a first wedgemember and a second wedge member, the screw extending through at least aportion of the first and second wedge member. The core member mayfurther include a sleeve coupled to one of the first and second wedgemembers, the sleeve defining a first expansion guide and a secondexpansion guide, the screw extending through at least a portion of thesleeve. The first and second expansion guides may extend from the sleevein opposite directions, the first expansion guide extending toward thefirst outer plate and the second expansion guide extending toward thesecond outer plate. Further, each expansion guide may include asubstantially diagonal edge, at least a portion of each expansion guidedefining a slot that is substantially parallel to the diagonal edge.Rotation of the screw may cause the core member to transition from afirst configuration to a second configuration, during which transitionthe first and second wedge members may move closer to each other and thefirst and second expansion bodies may move away from each other. Thedevice may further include a first tissue engagement element and asecond tissue engagement element; and a first center expansion armhingedly connected to the first tissue engagement element and a secondcenter expansion arm hingedly connected to the second tissue engagementelement, the first center expansion arm being receivable within the slotof the first expansion guide and the second center expansion arm beingreceivable within the slot of the second expansion guide when the coremember is transitioned from the first configuration to the secondconfiguration. Each of the first and second outer plates may define anopening, the first and second tissue engagement elements extendingthrough a corresponding opening when the device is in the secondconfiguration. Each expansion body may define a first diagonal portion,a second diagonal portion, and a center portion, the center portionbeing substantially horizontal relative to the first and second diagonalportions. At least a portion of the first wedge may be in contact withand slidable relative to the first diagonal portion of the each of thefirst and second expansion bodies, and at least a portion of the secondwedge may be in contact with and slidable relative to the seconddiagonal portion of each of the first and second expansion bodies.Further, each diagonal portion may include a ridge and each wedgeincludes a first groove and a second groove, the ridge of each diagonalportion being matable with a corresponding of the first and secondgrooves. Each wedge may include a locking mechanism that has aprotrusion and each ridge includes at least one opening, the protrusionbeing engageable with the at least one opening of a corresponding ridge.

In another non-limiting embodiment, a medical device for insertionbetween two adjacent vertebrae may include: a first outer platform and asecond outer platform, each of the first and second outer platformsbeing composed of a shape-memory material having a transformativetemperature, the device being in a first configuration at a firsttemperature and being in a second configuration at a second temperature,the second temperature being greater than the transformativetemperature; a core member including a first expansion body, a secondexpansion body, a first wedge member, and a second wedge member, thefirst expansion body being coupled to the first outer platform and thesecond expansion body being coupled to the second outer platform; and ascrew rotatably disposed within the core member, the screw passingthrough at least a portion of each of the first and second wedgemembers, rotation of the screw causing the first and second wedgemembers to move toward each other and the first and second expansionbodies to move away from each other. The core member may further includea sleeve coupled to one of the first and second wedge members anddisposed about at least a portion of the screw. Further, the sleeve maydefine a first expansion guide and a second expansion guide, the firstand second expansion guides extending from the sleeve in oppositedirections, the first expansion guide extending toward the first outerplate and the second expansion guide extending toward the second outerplate, each expansion guide including a substantially diagonal edge, atleast a portion of each expansion guide defining a slot that issubstantially parallel to the diagonal edge. The device may furtherinclude a first tissue engagement element and a second tissue engagementelement; and a first center expansion arm hingedly connected to thefirst tissue engagement element and a second center expansion armhingedly connected to the second tissue engagement element, the firstcenter expansion arm being receivable within the slot of the firstexpansion guide and the second center expansion arm being receivablewithin the slot of the second expansion guide when the first and secondwedge members move toward each other causing the device to transition toan expanded configuration, each of the first and second outer platesdefining an opening, the first and second tissue engagement elementsextending through a corresponding opening when the device is in theexpanded configuration.

In one non-limiting embodiment, a system for interbody spinal fusion mayinclude a medical device including a core member, a screw rotatablydisposed within the core member, and a first outer plate and a secondouter plate, each of the first and second outer plates being coupled toat least a portion of the core member, rotation of the screwtransitioning the medical device between a non-expanded configurationand an expanded configuration. The system may further include aninsertion device including a lumen sized to accommodate the medicaldevice therein when the medical device is in the non-expandedconfiguration.

In one non-limiting embodiment, a method of performing a medicalprocedure in an intervertebral space may include positioning a medicaldevice in the intervertebral space, the medical device including: a coremember; a screw rotatably disposed within the core member, rotation ofthe screw in a first direction causing the core member to expand androtation of the screw in a second direction causing the core member tocontract; and a first outer plate and a second outer plate each beingcomposed of a shape-memory material having a transformation temperature,and each being coupled to at least a portion of the core member, atemperature within the intervertebral space being greater than thetransformation temperature and causing the first and second outer platesto transition from a substantially curved configuration to asubstantially flat configuration; and rotating the screw to expand thecore member until each of the first and second outer plates is incontact with a portion of a vertebra.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1A shows a first access pathway to an intervertebral space, such asfor the insertion of a spine cage;

FIG. 1B shows a second access pathway to an intervertebral space, suchas for the insertion of a spine cage;

FIG. 2A shows a first embodiment of a spine cage in an unexpanded state;

FIG. 2B shows the first embodiment of a spine cage in an expanded state;

FIG. 3A shows a second embodiment of a spine cage in a partiallyexpanded state;

FIG. 3B shows the second embodiment of a spine cage in a fully expandedstate;

FIG. 4 shows a third embodiment of a spine cage in a fully expendedstate;

FIG. 5A shows a fourth embodiment of a spine cage in an unexpandedstate;

FIG. 5B shows the fourth embodiment of a spine cage in a partiallyexpanded state;

FIG. 5C shows the fourth embodiment of a spine cage in a fully expandedstate;

FIG. 6A shows a fifth embodiment of a spine cage in an unexpanded state;

FIG. 6B shows the fifth embodiment of a spine cage in a fully expandedstate; and

FIG. 7A shows a sixth embodiment of a spine cage in an unexpanded state;

FIG. 7B shows the sixth embodiment of a spine cage in a fully expandedstate; and

FIG. 8 shows a view of low-profile transvertebral screws insertedbetween adjacent vertebrae.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method, system, and device forperforming spinal fusion procedures with minimal anatomicalmanipulation. Referring now to the drawings in which like referencedesignators refer to like elements, FIGS. 1A and 1B show insertion of anexpandable spine cage. Of note, the device components have beenrepresented where appropriate by conventional symbols in the drawings,showing only those specific details that are pertinent to understandingthe embodiments of the present invention so as not to obscure thedisclosure with details that will be readily apparent to those ofordinary skill in the art having the benefit of the description herein.Moreover, while certain embodiments or figures described herein mayillustrate features not expressly indicated on other figures orembodiments, it is understood that the features and components of thedevice and system disclosed herein may be included in a variety ofdifferent combinations or configurations without departing from thescope and spirit of the invention.

Continuing to refer to FIGS. 1A and 1B, insertion of an expandable spinecage is shown. The system for insertion of a spine cage used in aninterbody fusion procedure generally includes a spine cage 10 and aninsertion device 12. The spine cage 10 may be transitionable from anunexpanded state to an expanded state, and shown and described ingreater detail in FIGS. 2A-5B. The insertion device 12 may be a cannulahaving an elongate, rigid distal portion 14 defining a lumen 16 sized toaccommodate the diameter of the spine cage 10 in an unexpanded state(for example, as shown in FIG. 1A) and to be positioned proximate anintervertebral space 18 for delivery of the spine cage 10.Alternatively, the insertion device 12 may be a cannula-like devicehaving an elongate, flexible distal portion defining a lumen 16 sized toaccommodate the diameter of the spine cage 10 in an unexpanded state(for example, as shown in FIG. 1B). In this embodiment, the flexibledistal portion 14 of the insertion device 12 may be steerable to allowfor complete site preparation before a medical procedure or precisepositioning of a spine cage and/or graft material, stem cells, or othermaterials or devices. As a non-limiting example, the distal portion 14may be steered using one or more pull wires, push rods, or othersteering mechanisms. In either embodiment, the distal portion 14 of theinsertion device 12 may be free of texture to reduce tissue, ligament,and/or bone damage in the area proximate the implantation site. Further,the insertion device may include an opening 20 at the distal tip of theelongated portion through which the spine cage 10 may be expelled.

The method may generally include placing the insertion device 12proximate the space 18 between the adjacent vertebrae 22 to be fused.For example, the insertion device 12 may be inserted posteriorly, forexample, between the transverse processes 24 or laminae 25 of adjacenttarget vertebrae 22. Once the distal tip 14 of the insertion device 12is adjacent to the intervertebral space 18, the insertion device 12 maybe used to expel the spine cage 10 into the intervertebral space 18. Forexample, the spine cage 10 may be expelled from the insertion device 12using a push rod, air pressure, hydraulic pressure, or other suitablemeans. Additionally, an insertion device 12 having a steerable distalportion 14, such as that shown in FIG. 1B, may be inserted in a uniquemanner, such as from a pedicle 26 of a first vertebra 22A into theintervertebral space 18 between the first vertebra 22A and an adjacentvertebra 22B (as shown in FIG. 1B). Unlike currently known methods thatsimply use a linear pathway (for example, a linear pathway following thetrajectory of a pedicle), this pathway avoids damaging the dura matter,spinal cord, or other sensitive non-target tissue while still allowingaccess to the intervertebral space within minimal anatomicalmanipulation. Further, the flexible insertion device 12 may be used tointroduce tools for preparing the intervertebral space for a medicalprocedure. For example, the insertion device 12 may be used to introducea flexible screw bit to produce an access pathway from a pedicle of onevertebra to the intervertebral space between the first vertebra and anadjacent vertebra. The steerable distal portion 14 of the insertiondevice 12 allows the user to create a curved or twisted pathway suitablefor an individual patient's anatomy and/or treatment needs. Once thepathway is drilled, the insertion device may be used to implant a devicesuch as a spine cage 10 and/or to introduce or deposit biological ornon-biological materials such as bone graft material, stem cells,antibiotics, plugs, or other materials. Further, this pathway 27 may beused to introduce or deposit such materials over the course of anextended treatment period (for example, twelve or sixteen weeks), suchas a treatment period following spine cage implantation during whichstem cells are deposited to encourage disc regeneration.

As mentioned, the insertion device 12 may be used for spine cageimplantation with minimal anatomical manipulation. The spine cage 10(such as those shown in FIGS. 2A-5B) may be inserted into the body inits unexpanded state, which has a diameter that may be significantlysmaller than currently used spine cages. For example, the diameter ofthe spine cage 10 in the unexpanded state may be such that the spinecage 10 may be used within an insertion device lumen 16 having anapproximately 8 mm diameter. As a non-limiting example, the spine cage10 may have a diameter in the unexpanded state of approximately 7 mm.Consequently, other than removal of at least a portion of the vertebraldisc, the present method requires only minimal manipulation and/orremoval of the spinal muscles, ligaments, and/or bone, if any, toaccommodate the insertion device and spine cage 10.

Referring now to FIG. 2A, a first embodiment of a spine cage 10 in anunexpanded state is shown. The spine cage 10 may generally include anexpansion screw 28, a core member 30, a plurality of cam plates 32, andfirst 34A and second 34B outer shape memory platforms. In the unexpandedconfiguration, the cam plates 32 may be in contact with the core member30 and each of the first 34A and second 34B platforms may be in contactwith at least one of the plurality of cam plates 32. In other words, thecam plates 32 may be sandwiched between the core member 30 and platforms34A, 34B. As a non-limiting example, the diameter of the spine cage 10may be approximately 8 mm or less.

The core member 30 may have a tubular configuration, and the expansionscrew 28 may be rotatably disposed within the core member 30. Further,the expansion screw 28 may have a hexagonal socket 36 in at least oneend. The expansion screw 28, core member 30, and cam plates 32 may becomposed of a rigid, durable, biocompatible material such as titanium.The outer platforms 34A, 34B, on the other hand, may be composed of ashape memory material such as Nitinol.

Referring now to FIG. 2B, a first embodiment of a spine cage 10 in anexpanded state is shown. The shape memory platforms 34A, 34B may bemanufactured such that the platforms have an original position as shownin the expanded configuration of FIG. 2B, and a deformed position withgreater curvature, as shown in the unexpanded configuration of FIG. 2A.Once the spine cage 10 has been inserted in the intervertebral space 18,the higher body temperature of the surrounding area may be above thetransformation temperature of the shape memory material, thereby causingthe platforms 34A, 34B to flatten out and/or unfold. This unfoldingcreates a wider footprint than the spine cage in the unexpanded state,which can add stability to the implant and provide a larger surface areaengagement with the superior endplate of one vertebra and the inferiorendplate of another vertebra (that is, the endplates of the vertebraebetween which the spine cage is positioned). Additionally, the eachplatform 34A, 34B may include at least a portion 38 that has a differentpresent shape memory configuration, such that these portions function assupport arms to displace the load (e.g., compressive force of the spine)from the platforms to the vertebral endplates (as shown in FIG. 2B).Further, each platform 34A, 34B may include one or more spikes orprotrusions (for example, as shown in FIG. 4 as reference number 64)that expand or are exposed as the shape memory platforms expand. Thesespikes or protrusions may enhance grip between the platforms and thevertebral endplates.

Even though the unfolding of the shape memory platforms enhances contactbetween the spine cage 10 and adjacent vertebrae 22, this expansion maynot provide sufficient distractive force between the vertebrae. In fact,it is not intended that the unfolding do so, as this may causeuncontrolled distraction. So, the cam plates 32 may be expanded toprovide a controlled gross distraction between adjacent vertebrae 22. Toexpand the cam plates 32, a tool may be matably inserted into thehexagonal socket 36 of the expansion screw 28 and rotated (for example,in the clockwise direction). The tool may be sized to be inserted intothe access pathway 27 created for the insertion device 12. The expansionscrew 28 may include eccentric threading on at least a portion of itsouter surface, such that rotation of the expansion screw 28 will advancethe eccentric threading farther into the core member 30, displacing oneor more cams 32 or base plates 40 coupled to the cam plates 32. Thus,rotational motion of the expansion screw 28 is translated into linearmovement (e.g., outward movement) of the cam plates 32. The expansionscrew 28 may be rotated, and the spine cage expanded, until the surgeonis satisfied that there is sufficient contact between the outerplatforms 34A, 34B and the vertebral endplates and/or that the vertebraeare sufficiently distracted.

One or more additional spine cages 10 may likewise be inserted in theintervertebral space 18. Once the one or more spine cages 10 have beenimplanted in the target site, graft material may be added to theintervertebral space surrounding the one or more spine cages. Closingthe insertion pathway 27 may be significantly easier and less traumaticthan in currently known methods of interbody spinal fusion, and less, ifany, bone removal is required (for example, removal of portions of thepedicles and/or laminae), thereby greatly facilitating patient recoverytime.

Referring now to FIG. 3A, a second embodiment of a spine cage 10 in apartially expanded state is shown. The spine cage 10 may generallyinclude an expansion screw 28, first 42A and second 42B wedges, first44A and second 44B expansion bodies, and first 34A and second 34B outershape memory platforms. The first 42A and second 42B wedges and first44A and second 44B expansion bodies may together make up the core member58. In the unexpanded or partially expanded configurations, the firstand second expansion bodies 44A, 44B are in contact with each other,whereas the first and second wedges 42A, 42B are a distance apart fromeach other. For example, the first expansion body 44A may include a flatportion 45A that is in contact with the flat portion 45B of the secondexpansion body 44B. Further, each of the wedges 42A, 44B may include anouter face 46A, 46B and each of the expansion bodies 44A, 44B mayinclude a first 48A, 46C and second 48B, 48D outer face (obscured fromview). When in the unexpanded or partially expanded configuration, theouter face 46A of the first wedge 42A may be coplanar with the firstouter face 48A of the first expansion body 44A and the first outer face48C of the second expansion body 44B, so as to create a first surface50A that is substantially circular. Likewise, when in the unexpanded orpartially expanded configuration, the outer face 46B of the second wedge42B may be coplanar with the second outer face 48B of the firstexpansion body 44A and the second outer face 48D of the second expansionbody 44B, so as to create a second surface 50B that is substantiallycircular. Further, each expansion body 44A, 44B may include asubstantially V-shaped cross section that includes two diagonal portions52A, 52B, 52C, 52D, with each diagonal portion including a flange 54A,54B, 54C, 54D (54B and 54D obscured from view) that fits within and isslidably disposed within a complementary groove 56A, 56B, 56C, 56D (56Band 56D obscured from view) of the adjacent wedge 42A, 42B.

The first and second wedges 42A, 42B and first and second expansionbodies 44A, 44B together may create a core member 58 that issubstantially tubular in shape, and the expansion screw 28 may berotatably disposed within the core member 58. For example, the expansionscrew 28 may extend through at least a portion of each of the first 42Aand second 42B wedges. Further, the expansion screw 28 may have ahexagonal socket, knob, or other configuration in at least one end(obscured from view), for example, as shown in FIGS. 2A and 2B. Rotationof the expansion screw 28 in a first direction may cause the core member58 to expand, and rotation of the expansion screw 28 in a seconddirection may cause the core member 58 to contract. The expansion screw28 and core member 58 may be composed of a rigid, durable, biocompatiblematerial such as titanium. The outer platforms 34A, 34B, on the otherhand, may be composed of a shape memory material such as Nitinol. In thepartially expanded configuration shown in FIG. 3A, the shape memoryplatforms 34A, 34B may be expanded (for example, as a result in thetemperature increase when the spine cage is implanted within thepatient's body), but the core member 58 is unexpanded. In the unexpandedstate, the spine cage of FIGS. 3A and 3B may resemble the unexpandedspine cage shown in FIG. 2A.

Referring now to FIG. 3B, a second embodiment of a spine cage 10 in anexpanded state is shown. As shown in FIG. 3A, the shape memory platforms34A, 34B may be manufactured such that the platforms 34A, 34B have anoriginal position as shown in the partially expanded configuration ofFIGS. 3A and 3B, and a deformed position with greater curvature (such asthe unexpanded configuration of FIG. 2A), as shown and described ingreater detail in FIGS. 2A and 2B. To expand the core member 58, a toolmay be removably coupled to the expansion screw 28 and rotated. The toolmay be inserted into the access pathway 27 created for the insertiondevice to access the spine cage 10 when the spine cage 10 is positionedin an intervertebral space 18. Rotation of the expansion screw 28 maydraw the first and second wedges 42A, 42B toward each other, thusdisplacing the first and second expansion bodies 44A, 44B away from eachother, as shown in FIG. 3B. As is also shown in FIGS. 3A and 3B, theflange 54A-54D of each diagonal portion 52A-52D of each expansion body44A, 44B may be slidably disposed within the complementary groove56A-57D of the adjacent wedge 42A, 42B. For example, the flange 54A ofthe first diagonal portion 52A of the first expansion body 44A and theflange 52C of the first diagonal portion 52C of the second expansionbody 44B may each be slidably disposed within a first 56A and second 56Bcomplementary groove of the first wedge 42A. Likewise, the flange 54B ofthe second diagonal portion 52B of the first expansion body 44A and theflange 52D of the second diagonal portion 52D of the second expansionbody 44B may each be slidably disposed within a first 56C and second 56Dcomplementary groove of the second wedge 42B. In this manner, movementof the first and second wedges 42A, 42B toward each other will displacethe first and second expansion bodies 44A, 44B, and thus expand thespine cage 10. It will be understood that the flanges and complementarygrooves may have any configuration suitable for expansion of the spinecage and are not limited to that shown herein. Additionally, the eachplatform 34A, 34B may include at least a portion 38 that has a differentpresent shape memory configuration, such that these portions function assupport arms to displace the load (e.g., compressive force of the spine)from the platforms to the vertebral endplates (as shown in FIG. 3B).Further, each platform 34A, 34B may include one or more spikes orprotrusions that expand or are exposed as the shape memory platformsexpand. These spikes or protrusions may enhance grip between theplatforms and the vertebral endplates.

Referring now to FIG. 4, a third embodiment of a spine cage 10 in anexpanded state is shown. The spine cage 10 of FIG. 5 is generallysimilar to that shown in FIGS. 3A and 3B. However, the spine cage 10shown in FIG. 4 may include expansion bodies 44A, 44B that each have,instead of a flattened portion, a ridged portion 60A, 60B. Further, eachexpansion body 44A, 44B may include a hollowed portion, such that theridged portion 60A, 60B is composed of two individual segments, as shownin FIG. 4. Alternatively, each expansion body 44A, 44B may be solid,such that each expansion body 44A, 44B includes only one ridged portion60A, 60B.

The outer platforms 34A, 34B of the spine cage 10 shown in FIG. 4 may becomposed of a shape memory material and may also include a plurality offingers 62A, 62B. The fingers 62A of the first outer platform 34A may beconfigured to be complementary to each other, such that when the spinecage 10 is in an unexpanded state and the platforms 34A, 34B are in adeformed position with greater curvature, the fingers 62A of the firstouter platform 34A alternate with the fingers 62B of the second outerplatform 34B. That is, at least one finger 62 of one platform 34 may bedisposed between two adjacent fingers 62 of the other platform 34. Theouter platforms 34A, 34B are shown in FIG. 4 in an original, expandedstate. The outer platforms 34A, 34B may further include one or morespikes or protrusions 64 that expand or are exposed as the shape memoryplatforms 34A, 34B expand. These spikes or protrusions 64 may enhancegrip between the platforms 34A, 34B and the vertebral endplates.Additionally, each platform 34A, 34B may include one or more screwconduits 66 that each extends through the platform 34 and through atleast a portion of the adjacent expansion body 44. Inserting a screwinto these conduits 66 may help secure the platforms 34A, 34B to theadjacent expansion body 44A, 44B. Additionally, each conduit 66 mayfurther extend into at least a portion of a wedge 42A, 42B, and a screwinserted into the conduit 66 may provide additional locking of the spinecage 10 in an expanded configuration.

Continuing to refer to FIG. 4, the core member 58 may include two wedges42A, 42B, each of which being engageable with the expansion screw 28(for example, similar to that shown and described in FIGS. 3A and 3B),and a sleeve portion 68. At least one wedge 42A, 42B may include thesleeve portion 68 that extends from the wedge (42B, as shown in FIG. 4)over at least a portion of the expansion screw 28. The spine cage 10 mayfurther include locking components 70A, 70B, 70C, 70D that areengageable with the expansion bodies 44A, 44B and the wedges 42A, 42B.Each locking component 70A-70D may include one or more protrusions 72that are each engageable with a corresponding opening 74 on theexpansion bodies 44A, 44B. As is shown and described in FIGS. 3A, and3B, rotation of the expansion screw 28 may cause the wedges 42A, 42B tobe drawn toward each other, the expansion bodies 44A, 44B are distractedfrom each other, thus expanding the spine cage 10. Movement of thewedges 42A, 42B relative to the diagonal portions 52A-52D of theexpansion bodies 44A, 44B may cause movement of the locking components70A-70D likewise. For example, each diagonal portion 52A-52D may includetwo grooves 76, and at least a portion of each locking component 70A-70Dmay be slidably disposed within a corresponding groove 76 in the flanges52A-52D of the expansion bodies 44A, 44B. The protrusions 72 on thelocking components 70A-70D, as they slide along the diagonal portions52A-52D of the expansion bodies 44A, 44B, may come into contact with andfit into the corresponding openings 74 of the expansion bodies 44A, 44B,thereby locking the wedges 42A, 42B and locking components 70A, 70D inplace and preventing further expansion or retraction of the wedges 42A,42B. As shown in FIGS. 4-5C, each expansion body 44 may include a centerportion located between the two diagonal portions 52, which may besubstantially horizontal relative to the diagonal portions 52. Theexpansion bodies 44 of the device shown in FIGS. 3A and 3B may also eachhave a center portion between the diagonal portions 52. These centerportions may be flat (for example, as shown in FIGS. 3A and 3B),textured, or including a series of troughs or other features (forexample, as shown in FIG. 4).

Referring now to FIGS. 5A-5C, a fourth embodiment of a spine cage 10 isshown. As shown in FIG. 5A, the spine cage 10 may be deliverable to anintervertebral space in an unexpanded configuration. In thisconfiguration, the spine cage 10 may have a substantially tubular shape,with the outer platforms 34A, 34B being in a deformed position withgreater curvature and substantially wrapping around the other componentsof the device. Thus, as is shown and described in the other embodiments,the spine cage 10 is deliverable in a configuration having a reduceddiameter, which reduces the amount of anatomical manipulation requiredfor implantation. As is similar to the spine cage 10 shown and describedin FIG. 4, the outer platforms 34A, 34B of the spine cage 10 shown inFIGS. 5A-5C may each include a plurality of fingers 62 that arecomplementary to the fingers 62 of the other platform 34. Further, eachplatform 34A, 34B may include a ridged or corrugated pattern 64 toenhance contact between the platforms 34A, 34B and adjacent vertebralendplates.

Referring now to FIG. 5B, the spine cage 10 is shown in an expandedstate. As shown, the shape memory platforms 34A, 34B may be manufacturedsuch that the platforms have an original position as shown in theexpanded configuration of FIGS. 5B and 5C, and a deformed position withgreater curvature, as shown in the unexpanded configuration of FIG. 5A.Once the spine cage 10 has been inserted in the intervertebral space 18,the higher body temperature of the surrounding area may be above thetransformation temperature of the shape memory material, thereby causingthe platforms 34A, 34B to flatten out and/or unfold. The functionalityof the spine cage 10 of FIGS. 5A-5C may be generally similar to that ofthe spine cage 10 shown and described in FIGS. 2A-4. Specifically,rotation of the expansion screw 28 may cause the two wedges 42A, 42B tobe drawn toward each other, which, in turn, causes the expansion bodies44A, 44B to move away from each other. However, the spine cage 10 ofFIGS. 5A and 5C may further include expansion arms 78A, 78B, 78C, 78Dthat are each rotatably connected to a wedge 42A, 42B at a connectionpoint 79. As shown in FIGS. 5B and 5C, for example, the first wedge 42Amay include a first 78A and second 78B expansion arm, and the secondwedge 42B may likewise include a first 78C and second 78D expansion arm.Each expansion arm 78 may be connected to the corresponding wedge 42such that the expansion arm 78 is rotatable about an axis that issubstantially orthogonal to the longitudinal axis of the spine cage 10.The spine cage 10 may further include a central post 80 and a centralpost base 82, and each expansion body 44, 44B may include a central postconduit 84A, 84B. The first 42A and second 42B wedges, first 44A andsecond 44B expansion bodies, the central post 80, and central post base82 may together make up the core member 58.

Referring now to FIG. 5C, the spine cage 10 is shown in a fully expandedstate. As is shown and described, for example, in FIGS. 3A, and 3B,rotation of the expansion screw 28 may cause the wedges 42A, 42B to bedrawn toward each other, the expansion bodies 44A, 44B are distractedfrom each other, thus expanding the spine cage 10. Movement of thewedges 42A, 42B relative to the diagonal portions 52A-52D of theexpansion bodies 44A, 44B may cause movement of the locking components70A-70D likewise. For example, the diagonal portion flange 54A-54D ofeach expansion body 44A, 44B may include a groove 76, and at least aportion of each locking component 70A-70D may be slidably disposed averat least a portion of the corresponding flange 54A-54D and within acorresponding groove 76. Although elements 70A-70D are referred to aslocking components, it will be understood that, in any configuration ofthe spine cage 10, that whereas locking components 70A-70D may functionto lock the wedges 42A, 42B in place, they may additionally oralternatively function to distract the expansion bodies 44A, 44B beyondthat distance possible by use of the wedges 42A, 42B alone. That is, thewedges 42A, 42B may be drawn toward each other to a point that is insideof the diagonal portions 52A-52D of the expansion bodies 44A, 44B, andthe locking components 70A-70D may instead remain in contact with thediagonal portions 52A-52D, thereby continuing to distract the expansionbodies 44A, 44B (for example, as is shown in FIG. 5C).

Continuing to refer to FIG. 5B, the central post 80 may extend betweenthe first 34A and second 34B outer platforms, in a direction that issubstantially orthogonal to the longitudinal axis of the spine cage 10.When the spine cage 10 is in an unexpanded state (as shown in FIG. 5A)or a partially expanded state (as shown in FIG. 5B), one end of thecentral post 80 may be slidably disposed within the post conduit 84A ofthe first outer platform 34A and the other end of the central post 80may be slidably disposed within the post conduit 84B of the second outerplatform 34B. Further, the central post 80 may be coterminous with thecentral post conduits 84A, 84B, as shown, for example, in FIGS. 5A and5B. As the expansion bodies 44A, 44B are distracted from each other byrotation of the expansion screw 28, the platforms 34A, 34B and expansionbodies 44A, 44B may also move toward the ends of the central post 80,such that the central post 80 becomes recessed within the central postconduits 84A, 84B (as shown in FIG. 5C). The central post base 82 maydefine the minimum distance between the two wedges 42A, 42B. That is, asthe wedges move toward each other with rotation of the expansion screw28, they may come in contact with the central post base 82 and thus beprevented from moving closer together. This may help ensure that theexpansion bodies 44A, 44B do not move so far away from each other thatthe central post 80 comes free of the central post conduits 84A, 84B.

The central post base 82 may include a protrusion 86 on either side. Theexpansion arms 78A-78D may have at least one curved edge that is incontact with at least a portion of a protrusion 86 as the wedges 42A,42B move toward and away from each other. As is shown in FIG. 5B, theexpansion arms 78 may be sickle-shaped, defining a wider base portionthat is coupled to one of the wedges 42, and a narrower, pointed tipportion. A portion of the tip of each expansion arm 78A-78D may be incontact with a protrusion 86, whereas a portion of each expansion arm78A-78D that is closer to the attachment point 79 may be in contact witha protrusion 86 when the spine cage 10 is in a fully expanded state. Asthe wedges 42A, 42B and, therefore, the expansion arms 78A-78D are drawntoward each other, the movement of the protrusions 86 along theexpansion arms 78A-78D causes the expansion arms to rotate at theconnection point 79 toward the outer platforms 34A, 34B. As is shown inFIG. 5C, one of the arms 78A, 78D connected to each wedge 42A, 42B onopposing sides of the device 10 may extend at least partially through anopening 88A in the first outer platform 34A. Likewise, one of the arms78B, 78C connected to each wedge 42A, 42B on opposing sides of thedevice 10 may extend at least partially through an opening 88B in thesecond outer platform 34B. Expansion of the spine cage 10 may occur oncethe spine cage is in the intervertebral space 18. As they extend throughthe openings 88A, 88B, the pointed tips of the expansion arms 78A-78Dmay dig into or otherwise contact and help anchor the spine cage 10 tothe endplates of adjacent vertebrae. Further, as the outer platforms34A, 34B expand, the fingers 62A, 62B and the ridged or corrugatedpattern 68 of the platforms 34A, 34B may also engage the endplates ofadjacent vertebrae.

Referring now to FIGS. 6A and 6B, a fifth embodiment of a spine cage 10in an unexpanded state and a fully expanded state is shown. As shown inFIG. 6A, the spine cage 10 may be deliverable to an intervertebral spacein an unexpanded configuration. In this configuration, the spine cage 10may have a substantially tubular shape, with the outer platforms 34A,34B being in a deformed position with greater curvature andsubstantially wrapping around the other components of the device (asshown in FIG. 6A). Thus, as is shown and described in the otherembodiments, the spine cage 10 is deliverable in a configuration havinga reduced diameter, which reduces the amount of anatomical manipulationrequired for implantation. As is similar to the spine cage 10 shown anddescribed in FIGS. 4-5C, the outer platforms 34A, 34B of the spine cage10 shown in FIGS. 6A and 6B may each include a plurality of fingers 62that are complementary to the fingers 62 of the other platform 34.Further, each platform 34A, 34B may include a ridged or corrugatedpattern 64 to enhance contact between the platforms 34A, 34B andadjacent vertebral endplates.

Referring now to FIG. 6B, the spine cage 10 is shown in a fully expandedstate. As shown, the shape memory platforms 34A, 34B may be manufacturedsuch that the platforms have an original position as shown in theexpanded configuration of FIG. 6B, and a deformed position with greatercurvature, as shown in the unexpanded configuration of FIG. 6A. Once thespine cage 10 has been inserted in the intervertebral space 18, thehigher body temperature of the surrounding area may be above thetransformation temperature of the shape memory material, thereby causingthe platforms 34A, 34B to flatten out and/or unfold. The functionalityof the spine cage 10 of FIGS. 6A and 6B may be generally similar to thatof the spine cage 10 shown and described in FIGS. 2A-5C. Specifically,rotation of the expansion screw 28 may cause the two wedges 42A, 42B tobe drawn toward each other, which, in turn, causes the expansion bodies44A, 44B to move away from each other. Like the spine cage 10 shown anddescribed in FIG. 4, the spine cage 10 in FIGS. 6A and 6B may include acore member 58 that includes two wedges 42A, 42B, each of which beingengageable with the expansion screw 28, and a sleeve portion 68. Atleast one wedge 42A, 42B may include the sleeve portion 68 that extendsfrom the wedge (for example, 42B, as shown in FIG. 6B) over at least aportion of the expansion screw 28. The spine cage 10 may further includelocking components 70A-70D that are engageable with the expansion bodies44A, 44B and the wedges 42A, 42B, as shown and described, for example,in FIGS. 4-5C.

Referring now to FIG. 6B, rotation of the expansion screw 28 may causethe wedges 42A, 42B to be drawn toward each other, thus causing theexpansion bodies 44A, 44B to be distracted from each other, expandingthe spine cage 10. Movement of the wedges 42A, 42B relative to thediagonal portions 52A-52D of the expansion bodies 44A, 44B may causemovement of the locking components 70A-70D likewise. For example, thediagonal portion flange 54A-54D of each expansion body 44A, 44B mayinclude a groove 76, and at least a portion of each locking component70A-70D may be slidably disposed aver at least a portion of thecorresponding flange 54A-54D and within a corresponding groove 76.

Continuing to refer to FIG. 6B, the spine cage 10 may include two ormore tissue engagement elements 90 (for example, vertebral engagementelements) that each extend through a corresponding opening in outerplatforms 34A, 34B as the device 10 is transitioned from a non-expandedconfiguration to an expanded configuration. Each tissue engagementelement 90 may include a notch 91 that is sized to accommodate a ridge92 in the corresponding expansion body 44A, 44B. The sleeve 68 mayinclude expansion guides 94, each of which extending in oppositedirections from the sleeve 68 toward one or the other of the outerplatforms 34A, 34B. As a non-limiting example, the expansion guides 94may each have a substantially triangular shape (for example, a righttriangle as shown in FIG. 6B), the base of which being coupled to orintegrated with the sleeve 68. Further, a center expansion arm 96 may behingedly connected to each tissue engagement element 90, such that thecenter expansion arms 96 are folded against the engagement elements 90,outer platforms 34A, 34B, and/or the expansion bodies 44A, 44B when thedevice 10 is in the unexpanded configuration. When the device 10 is inan expanded configuration, the center expansion arms 96 may hingeinward, toward the sleeve 68.

Each expansion guide 94 may include a substantially diagonal edge 98 anda slot 100 within each expansion guide 94. As shown in FIG. 6B, thediagonal edge may face the wedge 42 to which the sleeve 68 is notattached. For example, if the sleeve 68 is attached to the second wedge42B, the diagonal edge 98 may be on the side of the expansion guide 94that faces the first wedge 42A. Each center expansion arm 96 may bereceived within a corresponding slot 100 when the spine cage 10 is in anexpanded configuration. At least a portion of each slot 100 maysubstantially parallel to the diagonal edge 98, such that movement ofthe wedges 42A, 42B toward each other advances at least a portion ofeach center expansion arm 96 along the slot 100, from the sleeve 68toward the outer platforms 34A, 34B. This, in turn, may cause the tissueengagement elements 90 to extend beyond the outer platforms, 34A, 34B(that is, distally from the sleeve 68 and screw 28 beyond the outerplatforms 34A, 34B). Thus, as the expansion bodies 44A, 44B aredistracted from each other by rotation of the expansion screw 28, theplatforms 34A, 34B and expansion bodies 44A, 44B extension of the tissueengagement elements 90 toward each of the adjacent vertebrae may enhancecontact between the spine cage 10 and the adjacent vertebrae.

Referring now to FIGS. 7A and 7B, a sixth embodiment of a spine cage 10in an unexpanded state and an expanded state is shown. The spine cage 10may generally include first 34A and second 34B outer shape memoryplatforms and a plurality of shape memory coils 102 between the outerplatforms 34A, 34B. The shape memory platforms 34A, 34B may bemanufactured such that the platforms have an original position as shownin the expanded configuration of FIG. 7B, and a deformed position withgreater curvature, as shown in the unexpanded configuration of FIG. 7A.Likewise, the plurality of shape memory coils 102 may be manufacturedsuch that each coil has an original extended position as shown in theexpanded configuration of FIG. 7B, and a deformed, retracted position asshown in the unexpanded configuration of FIG. 7A. The stiffness value ofthe shape memory material from which the coils are manufactured may besuch that the coils 102 behave in a spring-like manner once implanted(that is, the shape memory coils may be flexible enough that they areable to compress, extend, and bend like a conventional spring). In theunexpanded configuration, each of the plurality of coils 102 may beretracted and the outer platforms 34A, 34B may be curved about theplurality of coils 102. In the expanded configuration, each of theplurality of coils 102 may be extended and the outer platforms 34A, 34Bmay be expanded. The spine cage of FIGS. 7A and 7B may preserve thepatient's range of spinal motion and provide a natural disc response.

Referring now to FIG. 8, a view of low-profile transvertebral screws 104inserted between adjacent vertebrae 22 is shown. Such screws 104 may beused to supplement a procedure such as an interbody fusion procedure. Asshown in FIG. 8, a screw 104 may be inserted into a pedicle 26 of onevertebra 22A and into the vertebral body 106 of an adjacent vertebra22B. The head 108 of the low-profile screw 104 may be countersunk intothe pedicle 26 so that no or a minimal portion thereof is exposed.Further, the screw 104 may include two discrete threaded portions 110with an unthreaded portion 112 therebetween. This prevents injury todisc or other intervertebral tissue by the screw threading when thescrews are in place. The surgeon may be provided with a variety ofscrews, each having a different distance that is unthreaded. Therequired unthreaded distance may be determined for each patient (such asby MRI imaging or the like) and the appropriate screw selected for use.

It will be understood that the devices, systems, and methods describedherein may be suitable for a variety of spinal procedures, including alateral transpsoas retroperitoneal approach (in which the devices shownand described herein may allow for substantially less risk oflumbo-sacral plexus injury and to associated neurological injuries), aunilateral or bilateral transforamenal approach (in which devices shownand described herein may allow for an intervertebral reduction, withminimal nerve retraction, bone removal, musculoskeletal or ligamentalinjury while maximizing intervertebral three-dimensional reconstructionand reduction), and a transpedicular transvertebral approach (in whichthe devices shown and described herein may cause no segmentalintervertebral musculoskeletal damage at all, may preserve the facetjoints and the muscular attachments, may maximize ligament strength, andmay spare the peripheral disc annulus and capsule while enabling a broadintradiscal expansion, which may serve as the basis for anintervertebral fusion or motion preserving intervertebral memory coildevice, acting as disc arthroplasty).

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention, which is limited only by the following claims.

What is claimed is:
 1. An intervertebral medical device, the medicaldevice comprising: a core member; and a first outer plate and a secondouter plate, each of the first and second outer plates being coupled toat least a portion of the core member, wherein the first and secondouter plates are composed of a shape memory material, the first andsecond outer plates being transitionable between a non-expanded,substantially tubular configuration and an expanded, substantiallyplanar configuration.
 2. The medical device of claim 1, wherein thefirst and second outer plates transition to the expanded configurationwhen the temperature of the first and second outer plates is greaterthan a transformative temperature of the shape memory material.
 3. Themedical device of claim 2, wherein the transformative temperature isless than the human body temperature of approximately 37 degreesCelsius.
 4. The medical device of claim 1, further comprising at leastone locking component configured to maintain at least one of the firstand second outer plates in the expanded, substantially planar position.5. The medical device of claim 4, wherein the at least one lockingcomponent is mechanically actuated by a rotational screw mechanism. 6.The medical device of claim 1, further comprising a plurality of fingersextending from a circumference of each of the first and second outerplates configured to anchor the medical device to adjoining vertebraltissue.
 7. The medical device of claim 1, wherein at least one of thefirst and second outer plates includes a plurality of protrusions on anexternal surface thereof to enhance a gripping characteristic of thedevice.
 8. The medical device of claim 1, wherein a distance between thefirst and second outer plates can be selectively adjusted to increase ordecrease an overall height of the medical device.
 9. A medical devicefor insertion between two adjacent vertebrae, the device comprising: afirst outer platform and a second outer platform, wherein a distancebetween the first and second outer platform is selectively adjustable toincrease or decrease an overall height of the medical device, whereineach of the first and second outer platforms is composed of ashape-memory material having a transformative temperature, the devicehaving a first, substantially tubular configuration at a firsttemperature less than the transformative temperature and having a secondconfiguration different from the first configuration at a secondtemperature greater than the transformative temperature.
 10. The medicaldevice of claim 9, wherein the transformative temperature is less thanthe human body temperature of approximately 37 degrees Celsius.
 11. Themedical device of claim 9, further comprising at least one lockingcomponent configured to maintain at least one of the first and secondouter plates in the second configuration, wherein the at least onelocking component is mechanically actuated by a rotational screwmechanism.
 12. A method of implanting a medical device, comprising:implanting the medical device between two vertebral bodies, wherein themedical device comprises: a core member; and a first outer plate and asecond outer plate, each of the first and second outer plates beingcoupled to at least a portion of the core member, wherein the first andsecond outer plates are composed of a shape memory material having atransformative temperature, wherein the first and second outer platestransition from a non-expanded, substantially tubular configuration toan unfurled, substantially planar configuration at the transformativetemperature.
 13. The method of claim 12, wherein the transformativetemperature is less than the human body temperature of approximately 37degrees Celsius.
 14. The method of claim 13, wherein implanting themedical device results in the first and second outer platestransitioning from the non-expanded, substantially tubular configurationto the unfurled, substantially planar configuration.
 15. The method ofclaim 14, further comprising selectively adjusting a distance betweenthe first and second outer plates to increase or decrease an overallheight of the medical device.
 16. The method of claim 15, whereinselectively adjusting a distance between the first and second outerplates includes rotationally engaging a portion of the medical devicewith an external instrument.
 17. The method of claim 15, furthercomprising engaging a locking element of the medical device to preventthe first and second outer plates from moving towards each other. 18.The method of claim 14, further comprising mechanically reinforcing thefirst and second outer plates in the unfurled, substantially planarconfiguration.
 19. The method of claim 12, wherein implanting themedical device includes inserting and positioning the medical devicebetween the two vertebral bodies through a lateral transpsoasretroperitoneal approach.
 20. The method of claim 12, wherein themedical device further comprises a plurality of protrusions on anexternal surface of at least one of first and second outer platesincludes to enhance a gripping characteristic of the medical device.